CORONAL MASS EJECTION: In addition to the many prominences on display around the sun today (see below), another form of solar activity has appeared. The Solar and Heliospheric Observatory is tracking a massive coronal mass ejection (CME) billowing away from the sun's western limb: movie. The slow-moving cloud will not hit Earth.

SOLAR ACTIVITY: "Solar minimum? No problem," reports Marco Vidovic of Stojnci, Slovenia. "Lately, every time I point my telescope at the edge of the sun, I see plenty of activity." He took this picture yesterday:

Vidovic uses a telescope equipped with an H-alpha filter tuned to the red glow of solar hydrogen. H-alpha filters are ideal for catching prominences--towering plumes of hydrogen held aloft by the sun's magnetic field. Because prominences are not rooted in sunspots, they do not vanish when the sunspot count plunges to zero.

Far from zero, the prominence count today is seven. Readers, if you have an H-alpha telescope, take a look at the solar activity that won't go away.

COMET Yi-SWAN: It's up all night long. Northern circumpolar Comet Yi-SWAN is gliding through the constellation Cassiopeia where it can be seen at almost any hour of the night through amateur telescopes. Working at his backyard observatory in Ellisville, Missouri, Gregg Ruppel took this picture on April 9th:

At the moment, the green, fuzzy comet is about as bright as an 8th-magnitude star--too dim for the naked eye. If predictions are correct, it will remain a telescopic comet, brightening only a little as it approaches the sun for a 190 million kilometer not-so-close encounter on May 8th. Astronomers will get a better look at the comet in the evenings ahead as the bright light of the full Moon fades.

Comet Yi-SWAN was co-discovered by amateur astronomers Dae-am Yi in Korea and Rob Matson in the USA. Yi photographed the comet himself using a Canon 5D and a 90 mm lens. Matson noticed it in images taken by the Solar and Heliospheric Observatory's SWAN sensor. Because of naming traditions (which should probably be modified) the comet bears SWAN's name, not Matson's.

This appears to be Comet Yi-SWAN's first visit to the inner solar system. A fresh comet exposed to intense sunlight for the first time can behave in unexpected ways. Will it grow a tail, fragment, brighten ... ? Stay tuned for updates.

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.